Different types of teeth stains can have different etiologies and consequently the way to remove them may also differ. Therefore in order to have the best cosmetic result you need to understand what type of stain is on your teeth so you know how to best remove them.
Table of Contents:
Types of tooth stains
There are really only two types of stains on teeth, extrinsic and intrinsic stains. That is the most common way to classify them but you can also categorize them based on when they developed and also their organicity.
Understanding these last two categorizations will give you a more comprehensive foundation for getting rid of the stains. They help explain how the stain removal treatments work.
Extrinsic vs Intrinsic
The simplest way to categorize teeth stains is based on their location or where they reside.
Extrinsic stains - located on the exterior of the tooth. These are attached to the outer surface of the enamel similar to barnacles on a boat.
Intrinsic stains - located on the interior of the tooth. They are below the surface of the enamel and are deeply embedded within the tooth.
Despite the differentiation between these two types, the vast majority of intrinsic stains begin as extrinsic ones. Over time when these stains on the exterior are not removed, they will slowly work their way into the tooth. They will enter into crevices or defects within the enamel and embed themselves in there to become intrinsic stains.
That is how they evade being removed by teeth cleanings and whitening toothpastes.
Type of Stain | Source | Treatment |
|---|---|---|
Green | Chromogenic bacteria and fungi | Tooth brushing and light polish |
Black | Iron in saliva | Deep teeth cleaning |
Orange | Chromogenic bacteria | Dental cleaning |
Brown | Tars from smoking, chewing, and dipping spit tobacco, food and beverages | Dental cleaning |
Topical medications | Stannous fluoride, chlorhexidine, cetylpyridinium chloride | Dental cleaning |
Yellow | Plaque | Tooth brushing |
Blue-green | Mercury and lead dust | Dental cleaning |
Red-black | Chewing betel nut, betel leaf, and lime | Dental cleaning |
Type of stain | Source | Treatment |
|---|---|---|
Dental fluorosis (white-spotted to brown-pitted enamel) | Excessive fluoride intake | Cannot be removed |
Hypocalcification | High fever during enamel formation | Cannot be removed |
Demineralization (white or brown spots on enamel, may be smooth or rough) | Acid erosion of enamel | Cannot be removed but recommend fluoride rinse |
Tetracycline (grayish brown discoloration) | Tetracycline use | Cannot be removed |
Age-related stains
Last but not least, most websites like to add in an additional category of stains called age related stains. They allege that these are attributed to getting older and your teeth naturally get more yellow as a result of it.
However that is incorrect because those are simply just extrinsic stains which have been given enough time to become intrinsic ones. These age related ones are simply a large accumulation of intrinsic stains over the years.
Just based on semantics, extrinsic and intrinsic stains are both descriptions based on location. Age is a descriptor for time and not for a location so it never really belonged in the first place!
Endogenous vs Exogenous
The discoloration of teeth could've also come during different times during tooth development.
Endogenous stains - these formed during the development of teeth while they haven't fully matured yet. You can think of these as true intrinsic stains.
Exogenous stains - this type was formed after the teeth were fully developed. The vast majority of these are extrinsic stains and also the ones that were left untreated and became intrinsic ones.
For the most part when people talk about having yellow teeth such as from drinking too much coffee, tea, and red wine they're referring to exogenous stains. The most common endogenous one would be tetracycline staining, which is incredibly difficult to remove. It's almost near impossible.
Organic vs Inorganic
Stains can be organic or inorganic in nature but for teeth they're all organic.
Organic stains - these molecules all have carbon in them and tend to come from natural food sources. This type of teeth stain can be whitened by chemical oxidation.
Inorganic stains - these molecules do not have carbon in them and tend to be synthetic. This stain type can be whitened via chemical reduction.
The organic stains are commonly found in coffee, tea, red wine, and food dyes. Basically any sort of staining food that you can think of that would yellow your teeth are pretty much organic in nature.
How to get rid of stains on teeth
The removal process depends on the type of stain on the tooth. We have multiple treatment options at our disposal to get rid of them. We can use mechanical means or chemical agents to get the job done.
Key points:
Extrinsic stains can be removed mechanically or chemically.
Intrinsic stains can only be removed chemically.
Mechanical removal
One of the simplest ways to get rid of extrinsic stains is by mechanically removing them.
Teeth cleanings at the dentist.
Brushing with whitening toothpaste at home.
Since extrinsic stains are located on the exterior of the tooth, it becomes a prime target for mechanical removal. The most effective way to remove these is by getting a professional dental cleaning. Your dentist will use an ultrasonic scaler and hand scalers to literally scrape these stains off the surfaces of your enamel. Afterwards the teeth will get polished to be smooth.
Unfortunately you can't go to the dentist everyday and most only go twice a year. That leaves it up to you to mechanically remove stains the other 363 days of the year. The best way to take care of this type of staining is by using a whitening toothpaste that has abrasives in it.
The abrasives within toothpaste give it grit and roughness which you can use to brush off the pesky stains on the enamel. Yes, that is literally how whitening toothpastes work. If you needed additional convincing, studies have shown that the functional whitening ingredient in toothpaste is the abrasive system.
Therefore it is the mechanically scrubbing action with an abrasive toothpaste that makes it "whitening". You may be thinking that it is not really "whitening" but it is. What you're probably thinking of is an in-office whitening session at the dentist but that is technically "bleaching" with chemical agents. That we will describe in the next section.
Oxidizing agent - Hydrogen peroxide
Chemical oxidation with hydrogen peroxide is probably what you were thinking of when the word whitening comes to mind. This is what your dentist uses at the office and is also what is in most OTC whitening products like the infamous whitening strips.
Chemical oxidation works very differently from mechanical removal of stains. The latter can only get rid of extrinsic stains since you can only brush the surface of your teeth. The former can remove intrinsic stains that are beneath the surface of your teeth because the chemical agents can diffuse into the tooth.
Studies have shown that hydrogen peroxide can diffuse through all of the tooth layers and oxidize all of the organic matrices. Since it is able to penetrate through the tooth, it can eliminate those pesky internally embedded stain molecules. It'll oxidize the extrinsic ones as well don't forget!
Examples of whitening products that oxidize stains on teeth:
Whitening mouthwash
Whitening strips
Whitening trays with or without LED lights
Take home kits from your dentist
In-office whitening sessions with or without light
Mechanism how hydrogen peroxide whitens teeth
To be more explicit, hydrogen peroxide is an unstable substance that readily decomposes into water, oxygen, and heat. However there are intermediate steps in that reaction which produce free radicals which are highly reactive. It is the interaction of these radicals with the stain molecules which whitens them.
Basically teeth stains are colored because they possess a lot of conjugated double bonds. The more of these double bonds in the stain the more light it absorbs and the more vibrant the color of the stain will be.
Essentially what the free radicals do is convert the double bonds into single bonds by adding oxygen to them. When the stain molecule loses the double bonds, it decreases light absorption and increases light reflection. In other words, it becomes lighter in color.
That is basically how your teeth become whiter when you oxidize it with hydrogen peroxide. As a matter of technicality, the stain never truly disappears from your teeth but they just become invisible looking to our eyes. This is in stark contrast to mechanical removal of extrinsic stains where you literally pulverize them from existence.
Also to tie it in for you, the peroxide will only oxidize the organic structures within the tooth. This is because oxidation reactions can only get rid of organic stains. Those conjugated double bonds are bonds from carbon to carbon after all!
Reducing agent - Sodium metabisulfite
Are you curious as to whether or not reduction agents (sodium metabisulfite) can bleach your teeth? Well, the purpose for the reducing agents is that they can get rid of inorganic stains.
These are stain molecules that do not have any carbon in them so the way to get rid of them will differ. If you try to oxidize these stains with peroxide, the color will never whiten.
Examples of inorganic stains:
Elements
Oxides
Mineral salts
Gemstones
Ink
We typically don't really eat these substances which is why our teeth don't really pick up these stains. That is why the most common chemical bleaching agent for teeth is peroxide and not sodium metabisulfite.
Nonetheless there was an interesting study which did try to use sodium metabisulfite to whiten teeth. It did work in lightening the color but we're curious as to where they found a person who was eating inorganic substances... Most people eat organic or whole foods you know.
Takeaway
For the most part you can basically think of extrinsic and intrinsic stains as the only two types of teeth stains. As long as you're able to distinguish between the two, you'll have a successful time in whitening your teeth.
Just remember that extrinsic stains can be removed via mechanical or chemical means. Intrinsic stains can only be whitened by chemical means because mechanical means have no effect on them.
